In recent years, a flat panel display using organic electro-luminescent devices (hereinafter, referred to as organic EL devices) has drawn attention. In particular, the organic EL device has advantages in that it has a low driving voltage and a high response speed and it is easy to increase the area thereof. Therefore, intensive research and development on a material and a device have been conducted.
Japanese Patent Application Laid-Open No. 2007-012359 discloses an organic electro-luminescent display apparatus including multi-color light emitting devices each having a plurality of top-emission organic EL devices stacked on each other. In addition, the organic electro-luminescent display apparatus includes active pixel circuits using thin film transistors (hereinafter, referred to as TFTs) provided on a substrate and an interlayer insulating film provided on the pixel circuit. One of a pair of electrodes of light emitting devices provided in the second and third layers is electrically connected to an output electrode of the TFT through contact holes formed in the first and second organic compound layers and the interlayer insulating film. The contact hole means a through hole that is formed by removing a portion of each layer of the display device and electrically connects the upper and lower layers.
In general, the organic EL device has a structure in which an organic compound layer with a thickness of 0.05 μm to 0.30 μm is interposed between electrodes. Therefore, light emitted from the light emitting layer is influenced by an optical interference effect between the electrodes.
In the display device disclosed in Japanese Patent Application Laid-Open No. 2007-012359, the wall of a contact hole formed in a first organic compound layer is inclined. A second organic compound layer is provided even in the contact hole. Therefore, the thickness of the second organic compound layer in the contact hole is different from that provided in a pixel region.
Therefore, since the second organic compound layer in the contact hole is also interposed between the electrodes, the second organic compound layer also emits light. That is, since the second organic compound layer has different thicknesses in the contact hole and in the pixel region, that is, the intensities of light emitted therefrom are different from each other due to an interference effect, the emission color varies.
In addition, the same problem as described above arises in the light emitting device provided in the third layer due to the contact hole provided in the second organic compound layer.